Method for producing epoxidated glyceride acetates

ABSTRACT

The invention relates to an improved method for producing epoxidated glyceride acetates. The inventive method involves transesterifying epoxy fatty acid esters with triacetin.

FIELD OF THE INVENTION

[0001] This invention relates to a process for the production ofepoxidized glyceride acetates in which epoxyfatty acid esters aretransesterified with triacetin.

PRIOR ART

[0002] In the processing, more especially the molding, ofhalogen-containing organic plastics, more particularly polyvinylchloride (PVC), additives are generally incorporated in the plasticswith the intention of performing certain functions. The additives may berequired to develop their effect during processing itself or to impartcertain properties to the moldings or workpieces thus obtained.

[0003] An important class of such additives which are widely used arethe so-called plasticizers. As well-known to the expert, the plasticizermarket has long been dominated by so-called phthalates or adipates.Dioctyl phthalate (DOP) and dioctyl adipate (DOA) in particular areroutinely used as plasticizers.

[0004] However, there has long been a need to replace the traditionalplasticizers mentioned, such as DOP or DOA, by plasticizers with adifferent structure. A technical solution to this problem was proposedin U.S. Pat. No. 2,895,966 published in 1959. This document proposesepoxidized monoglyceride diacetates, for example monoepoxystearyldiacetoglyceride, as plasticizers for plastics and states that, besidescertain stabilizing properties, compounds such as these in particularhave a plasticizing effect and, in addition, may readily be incorporatedin numerous plastics, i.e. are compatible with those plastics.

[0005] According to U.S. Pat. No. 2,895,966, the plasticizers areproduced by initially preparing monoglyceride diacetates based onunsaturated fatty acids and then subjected them to epoxidation. However,the plasticizers proposed in U.S. Pat. No. 2,895,966 were neversuccessfully used in practice. A major reason for this may lie in thefact that they are difficult to produce on an industrial scale.According to the technical teaching disclosed in U.S. Pat. No.2,895,966, an oil having a corresponding content of C═C double bonds inthe fatty acid units is first subjected to transesterification withglycerol, followed by acetylation and finally—in a third step—byepoxidation. After each process step, the crude product obtained iselaborately purified. More particularly, the crude product obtainedafter the transesterification with glycerol is washed with water toremove any soap formed and glycerol. The crude product obtained afteracetylation with excess acetanhydride is also washed with water in aninert gas atmosphere and then dried.

[0006] As for the rest, it is pointed out that the technical teaching ofU.S. Pat. No. 2,895,966 is specifically directed to monoglyceridediacetates. This is particularly apparent from the paragraph linkingcolumns 1 and 2. Although it is stated by way of limitation that complexmixtures of substances containing certain quantities of glycerides withonly one aceto group are normally present, it is directly and clearlydisclosed that monoglyceride diacetates in these mixtures are thecritical and quantitatively dominant species for the effect to beobtained and for solving the stated problem.

DESCRIPTION OF THE INVENTION

[0007] The problem addressed by the present invention was to provide animproved process for the production of plasticizers forhalogen-containing plastics of the epoxidized glyceride acetate type.Another problem addressed by the present invention was to provideactive-substance mixtures of epoxidized glyceride acetates not disclosedin the prior art which would be particularly suitable as plasticizingsubstances for PVC by virtue of their specific composition.

[0008] In a first embodiment, the present invention relates to a processfor the production of epoxidized glyceride acetates in which epoxyfattyacid esters are transesterified with triacetin.

[0009] Epoxidized Glyceride Acetates

[0010] In the process according to the invention, epoxyfatty acid estersare reacted with triacetin—a reaction which may be chemicallyinterpreted as transesterification. The product present after thisreaction need not necessarily be homogeneous in the sense of a singlemolecular structure. On the contrary, this product is generally a moreor less complex mixture of different chemical individuals. Nevertheless,such a mixture is also referred to as “epoxidized glyceride acetate” inthe present specification on pragmatic grounds. Depending on the desiredreaction ratio of the two reactants of the transesterification (seebelow), epoxidized monoglyceride diacetates or epoxidized diglyceridemonoacetates may represent quantitatively the dominant species of theproduct mixture.

[0011] Epoxyfatty Acid Esters

[0012] In the context of the present invention, epoxyfatty acid estersare understood to be:

[0013] a) Monoesters of fatty acids and monohydric alcohols with theformula R′—OH, where R′ is a C₁₋₁₈ alkyl group which may be saturated orunsaturated, linear or branched, aliphatic or cycloaliphatic, with theproviso that the fatty acid part derives from a C₈₋₂₄ fatty acid whichcontains at least one C═C double bond per molecule and with the furtherproviso that at least one C═C double bond per fatty acid unit is presentin epoxidized form.

[0014] b) Triesters of fatty acids and glycerol, with the proviso thatthe fatty acid components derive from C₃₋₂₄ fatty acids, with theproviso that at least 30% of the fatty acid units of the triesterscontain at least one C═C double bond and with the additional provisothat at least one C═C double bond per molecule of triester is present inepoxidized form.

[0015] The term “fatty acid” is familiar to the expert and is defined,for example, in the standard work Römpps Chemie-Lexikon (cf. 7thEdition, Stuttgart 1973, pages 1107-1110).

[0016] The compounds b) are triglycerides based on the fatty acidsmentioned and glycerol. The glycerides used may be syntheticallyproduced compounds or even fats and oils of natural origin (for adefinition of “fats and oils”, see for example Römpps Chemie-Lexikon,cf. 7th Edition, Stuttgart 1973, pages 1101-1106).

[0017] Preferably at least 50% and more particularly at least 80% of thefatty acid units of the triesters b) contain at least one C═C doublebond.

[0018] The proviso that at least one C═C double bond per molecule oftriester b) must be present in epoxidized form logically applies only tothose molecules of the triester in which at least one C═C double bond ispresent because, although a triester b) by definition contains a certainproportion of fatty acid units with at least one C═C double bond,particularly where it derives from fats and oils of natural origin,molecules whose fatty acid units are all saturated may also be presentin the triester on account of the statistical distribution.

[0019] Triacetin

[0020] Triacetin is characterized by the following structure:

[0021] Triacetin is a commercially available product of which theproduction has long been known. For example, DE-A-30 04 660 describes aprocess for the production of triacetin by reaction of glycerol withacetic acid and acetic anhydride.

[0022] Transesterification of Epoxyfatty Acid Esters With Triacetin

[0023] The process according to the invention represents atransesterification reaction. In this reaction, the oxirane rings(=epoxide groups) of the epoxyfatty acid esters remain intact.

[0024] The process according to the invention is preferably carried outin the presence of a transesterification catalyst. Transesterificationcatalysts are known to the expert. They are preferably basic compounds,such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodiummethylate, sodium ethylate, and also tin(IV) compounds such as, forexample, dibutyl tin dilaurate. The quantities of catalyst used arepreferably between 0.01 and 1.0% by weight, based on the total quantityof epoxyfatty acid esters and triacetin used, and more particularlybetween 0.05 and 0.2% by weight.

[0025] The process according to the invention is preferably carried outat reaction temperatures in the range from 120 to 240° C. and moreparticularly at reaction temperatures in the range from 150 to 230° C.

[0026] The reaction times in the process according to the invention arepreferably 1 to 6 hours and more particularly 3 to 5 hours.

[0027] The molar ratios of epoxyfatty acid esters and triacetin in theprocess according to the invention are preferably adjusted to values of1:2 to 2:1.

[0028] The epoxyfatty acid esters used in the process according to theinvention are, in particular,

[0029] epoxidized esters of fatty acids and monohydric alcohols of thetype a) defined in more detail above, the alcohol units of these estersbeing selected from the group consisting of methanol, ethanol, propanol,butanol and 2-ethylhexanol;

[0030] soybean oil epoxide, linseed oil epoxide, sunflower oil epoxide,rapeseed oil epoxide, tallow epoxide.

[0031] The present invention also relates to epoxidized glycerideacetates obtainable by transesterification of epoxyfatty acid esterswith triacetin in such a molar ratio that diglyceride monoacetates arequantitatively the dominant species in the product mixture. To this end,the molar ratios of epoxyfatty acid esters to triacetin are adjusted inthe transesterification reaction to values of, in particular, 1.1:1 to2:1.

[0032] The present invention also relates to the use of epoxidizedglyceride acetates, which are obtainable by transesterification ofepoxyfatty acid esters with triacetin in such a molar ratio thatdiglyceride monoacetates are quantitatively the dominant species in theproduct mixture, as plasticizers for halogen-containing organicplastics, more particularly PVC.

EXAMPLES

[0033] Substances used Name Explanation Vinnolit H 70 DF PVC (AdventInternational) Irgastab BZ 561 Ba/Zn stabilizer (Ciba-Geigy) Edenol D 81Epoxidized soybean oil (Cognis/DE) Stabiol CZ 222 Ca/Zn stabilizer(Cognis/DE) Loxiol G 10 Lubricant (Cognis/DE) Loxiol G 20 Lubricant(Cognis/DE) Dioctyl phthalate Plasticizer (Degussa-Hüls/DE) Dioctyladipate Plasticizer (Degussa-Hüls/DE)

PRODUCTION EXAMPLES Example I

[0034] Transesterification of Oleic Acid Methyl Ester Epoxide WithTriacetin

[0035] 145 g triacetin were transesterified with 205 g oleic acid methylester epoxide (epoxide content 4.9%) at 150° C. in the presence of 1.8 gsodium methylate as catalyst. The reaction time was 3 hours. Ca. 30 gacetic acid methyl ester were distilled off as secondary product. 320 gglycerol monoepoxyoleate diacetate were obtained. This product had thefollowing characteristics: acid value (AV): 0.97 saponification value(SV): 390 epoxide content: 3.1%

[0036] If desired, the color of the product may be improved by bleachingwith ca. 2 g hydrogen peroxide (30%).

Example 2

[0037] Transesterification of Epoxidized Soybean Oil With Triacetin

[0038] 340 g epoxidized soybean oil (Edenol D 81) were transesterifiedwith 161 g triacetin at 220° C. in the presence of 0.25 g sodiumhydroxide as catalyst. The reaction time was 4 hours. To improve itscolor, the product was bleached with ca. 2 g hydrogen peroxide (30%).Ca. 500 g glycerol monoepoxyoleate diacetate were obtained. This producthad the following characteristics: AV: 0.86 Lovibond color 1″: yellow:5.6, red: 1.0 epoxide content: 4.1%

Example 3

[0039] Transesterification of Epoxidized Soybean Oil With Triacetin

[0040] 340 g epoxidized soybean oil (Edenol D 81) were transesterifiedwith 161 g triacetin at 220° C. in the presence of 0.25 g dibutyl tindilaurate as catalyst. The reaction time was 3 hours. To improve itscolor, the product was bleached with ca. 1 g hydrogen peroxide (30%).Ca. 500 g glycerol monoepoxyoleate diacetate were obtained. This producthad the following characteristics: AV: 1.2 Lovibond color 1″: yellow:6.2, red: 1.0 epoxide content: 4.0%

APPLICATION EXAMPLES

[0041] Formulations F1 to F8 based on various plasticizers were producedfor performance testing. The composition of these formulations is shownin the following Table.

[0042] The quantities in which the individual components are used areexpressed in “phr” which stands for parts per hundred resin andindicates how many parts by weight of the particular substance arepresent in the PVC after addition of the composition, based on 100 partsby weight PVC. Accordingly, the formulations all contain 100 parts PVC(Vinnolit H 70 DF).

[0043] It is specifically pointed out that, in the case of F1 to F8, itis important to distinguish between the overall formulations, which areused for performance testing and which contain all the componentsmentioned, and the actual additive compositions which contain all thecomponents mentioned except for the PVC. F1 F2 F3 Vinnolit H 70 DF 100100 100 Irgastab BZ 561 1.5 1.5 1.5 Dioctyl phthalate 100 0 0 Dioctyladipate 0 100 0 Compound of Example 1 0 0 100 F4 F5 F6 Vinnolit H 70 DF100 100 100 Edenol D 81 8 8 8 Stabiol CZ 2222 1 1 1 Loxiol G 10 2.5 2.52.5 Loxiol G 20 0.2 0.2 0.2 Dioctyl phthalate 30 0 0 Compound of Example2 0 30 0 Compound of Example 3 0 0 30 F7 F8 Vinnolit H 70 DF 100 100Edenol D 81 8 8 Stabiol CZ 222 1 1 Loxiol G 10 2.5 2.5 Loxiol G 20 0.20.2 Dioctyl adipate 50 0 Compound of 0 50 Example 3

[0044] Strips were produced on the basis of formulations R1 to R8 andwere tested for static thermal stability at 180° C. The strips wereproduced by homogenizing and plasticizing the formulations mentioned for5 mins. at 170° C. on laboratory rolls. Test specimens measuring 17×17mm were cut out from the ca. 0.5 mm thick strips thus produced.

[0045] The following measurements were carried out with the testformulations:

[0046] Stability test at elevated temperature: strips were produced fromthe formulations and tested for static thermal stability at 180° C. Thestrips were produced by homogenizing and plasticizing the components ofthe formulations mentioned for 5 mins. at 170° C. on laboratory rolls.Test specimens measuring 17×17 mm were cut out from the ca. 0.5 mm thickstrips thus produced. The test specimens arranged on glass plates wereplaced on rotating shelves in a heating cabinet at 180° C. and removedat 15-minute intervals until all the test specimens were “burnt” (i.e.had turned black in color).

[0047] Color measurement of strips: in addition, the L*, a*, b* methodknown to the expert (cf. DIN 6174) was applied to the strips for furthercharacterization. The initial color of the strip (yellowness value b*)was determined. A commercially available instrument (“Micro Color”,manufacturer: Dr. B. Lange) was used for the measurements.

[0048] Shore A hardness: the Shore A hardness of the strips as known tothe relevant expert was determined to DIN 52505 using a commerciallyavailable Shore hardness tester (manufacturer: Zwick).

[0049] Light transmission: the light transmission of 4 mm thick pressedplates based on the formulations mentioned was determined. The pressedplates were produced from the strips. The strips were pressed betweentwo pressing plates of a laboratory press (Collin) with spacers inbetween to form plates with the thickness mentioned. In the testscarried out, 8 strips each 0.5 mm thick were pressed at 170° C./250 barto form a 4 mm thick pressed plate.

[0050] Compatibility: by compatibility is meant the compatibility of theadditive compositions with the plastic (PVC). The compatibility of thestrips was determined after storage at room temperature. The strips weretested for compatibility by visual examination. The surface of the stripwas evaluated for signs of exudation. In this method, serious exudationis an indicator of serious incompatibility; the absence of exudation isan indicator of very good compatibility.

[0051] The results obtained with the test specimens are set out in thefollowing Table. C1 is a test specimen based on additive composition R1,C2 is a test specimen based on additive composition F2, etc. C1 C2 C3Thermal stability (180° C.) 75 mins. 60 mins. >270 mins. Shore Ahardness 61   58   65   Transparency (light transmission in %, 83   76  83   4 mm pressed plate) Compatibility after production Very good, noVery good, no Very good, no exudation, exudation exudation Compatibilityafter 6 months (storage Very good, no Very good, no Very good, no atroom temperature) exudation exudation exudation Compatibility after 12months (storage Very good, no Very good, no Very good, no at roomtemperature) exudation exudation, exudation C4 C5 C6 Thermal stability(180° C.) 90 mins. 210 mins. 210 mins. Shore A hardness 90   93   93  Initial color of the strip (yellowness 4.7 6.3 5.8 value b*)Compatibility after production Very good, no Very good, no Very good, noexudation, exudation exudation Compatibility after 18 months (storageVery good, no Very good, no Very good, no at room temperature) exudationexudation exudation C7 C8 Thermal stability (180° C.) 75 mins. 240 mins.Shore A hardness 73   80   Initial color of the strip (yellowness 2.64.3 value b*) Compatibility after production Very good, no Very good, noexudation exudation Compatibility after 10 weeks (storage Very good, noVery good, no at room temperature) exudation exudation,

1. A process for the production of epoxidized glyceride acetates,characterized in that epoxyfatty acid esters are transesterified withtriacetin.
 2. A process as claimed in claim 1, characterized in that theepoxyfatty acid esters used are triesters of fatty acids and glycerol,the fatty acid components of these triesters deriving from C₃₋₂₄ fattyacids, with the proviso that at least 80% of the fatty acid units of thetriesters contain at least one C═C double bond and with the additionalproviso that at least one C═C double bond per molecule of triester ispresent in epoxidized form.
 3. A process as claimed in claim 1 or 2,characterized in that the transesterification is carried out in thepresence of a transesterification catalyst.
 4. A process as claimed inclaim 3, characterized in that the catalyst is used in a quantity of0.01 to 1.0% by weight, based on the total quantity of epoxyfatty acidester used and triacetin.
 5. A process as claimed in any of claims 1 to4, characterized in that the reaction temperature is adjusted to a valueof 120 to 240° C.
 6. A process as claimed in any of claims 1 to 5,characterized in that the reaction time is adjusted to a value of 1 to 6hours.
 7. A process as claimed in any of claims 1 to 6, characterized inthat the molar ratios of epoxyfatty acid esters to triacetin areadjusted to values of 1:2 to 2:1.
 8. Epoxidized glyceride acetatesobtainable by transesterification of epoxyfatty acid esters withtriacetin in such a molar ratio that diglyceride monoacetates arequantitatively the dominant species in the product mixture. 9.Epoxidized glyceride acetates as claimed in claim 8, characterized inthat the molar ratios of epoxyfatty acid esters to triacetin areadjusted to values of 1:2 to 2:1.
 10. The use of epoxidized glycerideacetates obtainable by transesterification of epoxyfatty acid esterswith triacetin in such a molar ratio that diglyceride monoacetates arequantitatively the dominant species in the product mixture asplasticizers for halogen-containing organic plastics.